Abstract: On the basis of analyzing the causes of waterlogging and the overall regional defense capacity of Jiangbei urban district of Hangzhou City, we present urban encirclement schemes to optimize the drainage pattern in the hope of offering reference for the decision-making of flood control planning and regulation. At present in Hangzhou we already have a series of flood control and drainage projects including the comprehensive water resources planning for Hangzhou, Jiaxing, and Huzhou region (hereafter referred to as Hang-Jia-Hu region), the urban flood control and disaster reduction planning for Hangzhou City, the special planning of west Hangzhou Kechuang corridor, and others. Under such background, we established the one-dimensional unsteady flow mathematical model of flood control for the eastern plain of Hang-Jia-Hu region, and calculated the implementation effect and impacts of three urban encirclement schemes involving different arrangements of canals and control gates. Results show that by constructing sluices and pumps along the north control line and together with optimizing operation, the Jiangbei urban district of Hangzhou City could meet drainage standards and actively prevent from waterlogging on one hand, and reduce the flood control pressure on downstream areas to the greatest extent and take into account the flood control of the river basin on the other. The research finding is of referential value for the flood control and drainage of cities in the middle and upper reaches of the eastern Hang-Jia-Hu plain.

Key words: drainage pattern, optimized scheduling, urban encirclement, mathematical model, drainage standard, Jiangbei urban district of Hangzhou